Sasuke would be a great character to include. His brooding nature and powerful Sharingan abilities would contrast with the more carefree Yoruichi. He could have some sort of rivalry or begrudging respect for Yoruichi's skills. And his relationship with Naruto would add another layer of drama to the crossover, as they could have different opinions on how to deal with the new situations in the Bleach world.
Madara Uchiha could be a great antagonist. He could have somehow gained the power to cross into the Bleach universe and is causing trouble there. Yoruichi and Naruto would have to put aside their differences and combine their skills to stop him. Madara's powerful jutsu and his desire for power would make him a formidable foe for the duo.
Well, perhaps in the fanfic, Naruto and Yoruichi are brought together by a mysterious force that binds their destinies. They might start off as strangers but gradually learn to trust and rely on each other. For example, Yoruichi could be on a mission in the Naruto world and Naruto helps her out. In return, she offers to train him in stealth and agility, skills she is highly proficient in.
Perhaps in this crossover fanfiction, there is a prophecy in both the Naruto and Bleach worlds about a combined force that can save the multiverse from a great evil. Naruto and Yoruichi are the key components of this prophecy. At first, they don't get along as they have very different personalities and ways of doing things. Naruto is more straightforward and brash, while Yoruichi is sly and mysterious. But as they face challenges together, they learn to work as a team and combine their powers of ninjutsu and shinigami abilities to defeat the ultimate threat.
He could possess the power of the Rasengan. Yoruichi could potentially use it in different forms, like a long - range Rasengan blast or a more concentrated, close - range version for melee combat. And maybe Naruto's chakra nature could also be incorporated, allowing Yoruichi to use wind - based attacks more effectively.
There could be many interesting fanfictions involving Naruto and Yoruichi. One possibility is that they could be from different universes but are brought together by some sort of magic or interdimensional rift. In the fanfiction, they might start as rivals, each with their own set of skills. Naruto's ability to use chakra and his ninja techniques like the Rasengan, and Yoruichi's incredible speed and shunpo ability. As the story progresses, they could learn from each other and develop a deep friendship. They might also team up to face a common enemy that threatens both of their worlds.
One plot could be that Yoruichi gets lost in the Naruto universe. Naruto finds her and, being the helpful person he is, offers to help her find her way back home. Along the way, they encounter various challenges. They might have to face off against some of Naruto's enemies who see Yoruichi as an unknown threat. As they overcome these challenges, they develop a bond. Yoruichi might teach Naruto some of her unique skills, and Naruto could show Yoruichi the importance of having a strong community, like his village, which is something she might not have in her own world.
A possible storyline is that Yoruichi discovers a way to travel to the Naruto universe due to some strange rift in the dimensions. She meets Naruto when he is still a young outcast in the village. Yoruichi, seeing his potential, decides to help him secretly. This leads to Naruto developing some new and unexpected abilities, which confounds his teachers and makes him an even more formidable ninja as he grows up.
Yoruichi has her unique cat - like abilities in the Bleach universe. If combined with Naruto's shadow clone jutsu, they could create some really interesting combat strategies. The shadow clones could be used to distract enemies while Yoruichi sneaks up on them with her stealth. And Naruto could use Yoruichi's knowledge of reiatsu (equivalent to chakra in a way) to better understand his own chakra limits and how to break through them.
Another theme is the exploration of their past. Their shared history in Soul Society is rich, and fanfics tend to dig into it. They might show how their past experiences have shaped their current relationship, like how they trained together in the past and how that affects their present interactions.